A growing number of parents are confused about whether to vaccinate their children, with many influenced by "anti-vax" material on social media. Can asking experts questions help one undecided couple find clarity?
"We're undecided but are swaying towards not getting the baby vaccinated," Mark tells the BBC's Victoria Derbyshire programme.
He and his wife, Victoria, are expecting their first child in August but he is stepfather to her two teenage children, who are both vaccinated.
Experts say the MMR vaccine is safe and has been given to millions of children worldwide.
But NHS England fears "vaccination deniers" are gaining traction on social media, with half of parents with young children being exposed to anti-vaccination content.
Mark and Victoria say they have been researching the topic mostly online.
"People tend to take things at face value," he says. "You've got a professional who says something and you take that as being [true].
"But it's good to do your own research and go out there and question the questions or question the answers, no matter where it's coming from."
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They are not alone.
Figures from data company SEMrush, seen by the programme, show a 296% increase in searches about the measles, mumps, and rubella virus (MMR) vaccine in the past 12 months in the UK, while the search term "anti-vaccine" has increased by 171%.
The number of two-year-olds having the MMR vaccine in England is at its lowest in eight years, with 91.2% vaccinated last year.
In 2018, there were 966 confirmed measles cases in England, nearly four times as many as the total number confirmed the previous year.
Victoria and Mark met Prof Beate Kampmann, director of the Vaccine Centre at the London School of Hygiene and Tropical Medicine, to ask her about one of their prime concerns.
"Why do you think it's acceptable to inject aluminium into babies when it's being banned in things such as aerosols?" asks Mark.
Prof Kampmann says many people are concerned about the extra ingredients in vaccines.
"Alum is a very important part of the vaccines because it actually helps the stuff that's really important in the vaccine, which is the bacterial viral ingredients, to work well in the body," she says.
"You make it sound like we're giving a massive shot of aluminium to the body... - that's not at all the case.
"The concentration is only a 1,000th of what you'd find in the natural environment and what we already have in our bodies."
Mark says the information leaflets in vaccine packaging are not always offered to parents before injections. And some he and Victoria have seen say they should not be administered if the child is allergic - but how would parents know?
Prof Kampmann says the main allergy concern is some vaccines, such as MMR, contain traces of egg.
"You know if you have a demonstrated egg allergy," she says.
"You should be pointing that out.
"And by the time the baby gets that particular vaccine, you would know if they did... or not because they would have had egg in all sorts of products."
Dr Julian Spinks, of Court View medical practice, in Rochester, addresses another of the couple's concerns - why GP surgeries are paid for each vaccination.
"We're just wondering whether GPs are pressurised to meet targets for financial gain?" Mark says.
Dr Spinks says they do have some targets but the money involved is relatively small.
"The amount of money we get for a vaccine is about £10," he says.
"By the time you've covered the costs we have, which is recording people, paying for nurses and people and so on, well over half of that is gone.
"So actually, realistically, it's a very small amount of money we get."
Optional not compulsory
Mark and Victoria are also worried the NHS may be too quick to offer vaccinations - without fully explaining potential risks.
Dr Spinks says: "I don't think information is being suppressed as such [but] maybe people could get more.
"One of the difficulties is that a lot of the anti-vaccination sites will raise very obscure things, which it would be impossible to cover in a short leaflet.
"It doesn't mean we won't answer questions."
Mark then asks: "Why is it not fully explained to parents that immunisations are optional?"
And Dr Spinks says he always tells parents they are voluntary, even though he would very strongly recommend them.
"It ultimately is the parents' choice," he says, "but I do have concerns because I do believe immunisation protects and it's protecting your child and it's also protecting the children around them, because of this thing of actually suppressing spread of the virus from one child to another."
Mark and Victoria say meeting Prof Kampmann and Dr Spinks was "enlightening and informative".
"We were pleased that the professionals could empathise," Mark says, "and some felt there needed to be more info out there and training for health professionals.
"Hopefully other parents now feel comfortable to come forwards."